The collision now process momentums more appropriately; Velocity after collision is now determined by both weight of the unit, direction of movement, as well as the speed the other unit hit it at. Impatient unit also keep trying to obtain new navigation path to get itself out of the situation.
There seem to be a bug involved division by zero when there are too many units colliding with each other. Have to chase that out later.
Should I try going for Hexgrid implementation, or other AI things first?